Bump actions/checkout from 5 to 6

Author: kostis

.github/workflows/codespell.yml

@@ -4,7 +4,7 @@ jobs:
   codespell:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: codespell-project/actions-codespell@master
       with:
         path: .

.github/workflows/shellcheck.yml

@@ -4,5 +4,5 @@ jobs:
   shellcheck:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ludeeus/action-shellcheck@master